I have a 1995 jeep grand chrokee with a 4.0 have a problem with it starting when it is cold the ignition has to stay on for at least an hour before it will finally start you do not have to crank it just turn the key on have replaced plugs, wires, cap rotor, pick up coil, crank sensor and have cleaned all grounds need advice

When you crank the engine over when it's not starting, do you have spark? If so, start thinking about fuel. If you spray carb cleaner into the throttle body when cranking does it start? If so, you either have a fuel pump that isn't working correctly or an obstructed fuel filter.
Back to spark...If you don't have spark you may have a poor connection somewhere in the system or a lazy relay that is taking time to connect, in which case, the only real way to find it is to begin checking voltage everywhere. I'd also check the intake manifold temp sender and coolant sender for proper readings, though usually it will start but run poorly if one of those is out of range. You can get fairly decent test procedures in both chiltons or haynes...better and less expensive than guessing! (I believe that haynes calls the cam sensor a "stator" and lists it outside the ignition system electronics. I don't think that is your problem but it does not hurt to check!)
Good luck!